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Production of spin-polarized radioactive-ion beams via the projectile fragmentation reaction

XII th International Workshop on Polarized Sources, Targets & Polarimetry PSTP2007, Sept. 10-15 at Brookhaven National Laboratory. Production of spin-polarized radioactive-ion beams via the projectile fragmentation reaction. H. Ueno, A. Yoshimi, T. Nagatomo, T. Sugimoto, Y. Kobayashi

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Production of spin-polarized radioactive-ion beams via the projectile fragmentation reaction

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  1. XIIth International Workshop on Polarized Sources, Targets & Polarimetry PSTP2007, Sept. 10-15 at Brookhaven National Laboratory Production of spin-polarized radioactive-ion beams via the projectile fragmentation reaction H. Ueno, A. Yoshimi, T. Nagatomo, T. Sugimoto, Y. Kobayashi H. Watanabe, M. Ishihara Tokyo Institute of Technology K. Asahi, D. Nagae, M. Takemura, K. Shimada, K. Takase, T. Inoue, G. Kijima, T. Arai, S. Suda, S. Kagami, N. Hatakeyama Rikkyo University J. Murata, H. Kawamura D. Kameda RIKEN Nishina Center

  2. PSTP2007 Sept. 10-15 at BNL Outline • What is Projectile Fragmentation reaction? • Production of spin-polarized fragments in PF reaction • Mechanism • Feature of polarization phenomena in PF reaction • Application of polarized Radioactive-Ion (RI) beams • Nuclear moment measurements in RIKEN • Summary

  3. PSTP2007 Sept. 10-15 at BNL projectile target projectile fragment J. Gosset et al., Phys. Rev. C16 (1977) 629. Projectile Fragmentation Reaction Typical velocity of projectile nucleus: Fermi velocity of nucleus: Geometrical overlap is the essential part Projectile Thickness of the overlap region [fm-2 ] Powerful source of producing RI beams: LISE/GANIL, A1900/NSCL, FRS/RFS, RIPS/RIKEN, … Overlap Target

  4. PSTP2007 Sept. 10-15 at BNL Fragment-induced spin polarization K.Asahi et al., PLB 251, 499 (1990) fragment Sum of the lost Fermi momenta projectile P R Position vector of the participant portion -P DL=-RxP target Angular momentum left in the fragment part Goldhaber distribution: kinematical model: Projectile rest flame: Spectator rkspec. 0 Pspec. Rspec. Rparti rj parti Participant DL LF = 0

  5. PSTP2007 Sept. 10-15 at BNL First observation K. Asahi et. al., Phys. Lett. B 251 (1990) 488

  6. PSTP2007 Sept. 10-15 at BNL Detector near-side trajectory far-side trajectory Small-Z target Large-Z target 14N+79Au 15N+Au 15N+41Nb 15N+13Al 15N+Nb 12B 13B 13B 13B 13B Detector Dependence of polarization on Targets H. Okuno et al., PL B335,29 (1994)

  7. PSTP2007 Sept. 10-15 at BNL Projectile-fragmentation induced polarization • The polarization is typically 1~10 %, but strongly depends on • the emission angle and outgoing momentum of the fragments • target-Z numbers ( competition of far-side and near-side trajectories) • removed-nucleon numbers Advantages on applications : • Fastest method • Chemical independent Data are taken from “Table of nuclear magnetic dipole and electric quadrupole moments”, N.J. Stone, 2001 excited states ground states

  8. PSTP2007 Sept. 10-15 at BNL Study of the p- and sd- shell nuclei through their nuclear moments TITech / RIKEN Osaka / RIKEN • g-Factors measured at RIKEN • Boron isotopes : 14B, 15B, 17B • Carbon isotopes : 9C, 15C, 17C • Nitrogen isotopes : 17N, 18N, 19N • Oxygen isotopes : 13O • Fluorine isotopes : 21F • Aluminum isotopes : 23Al, 30Al, 32Al • Q-moments measured at RIKEN • Boron isotopes : 14B, 15B, 17B • Nitrogen isotopes : 18N • Oxygen isotopes : 13O • Magnesium isotopes : 23Mg • Aluminum isotopes : 31Al, 32Al Spin-parity assignment Effect of neutron excess on the magnetic moment Reduction of E2 effective charges Study on the island of inversion

  9. Neutron-rich Al isotopes- northern-side of the island of inversion- good examples PSTP2007 Sept. 10-15 at BNL I = 0 g-factor known N=20 μ or Q known (a few years ago)

  10. PSTP2007 Sept. 10-15 at BNL 30Al 32Al Yield (a. u.) (p-p0)/p0 (%) (p-p0)/p0 (%) θLab[AAl]≧1.3° 93Nb target t=150, 450μm 40Ar E=95AMeV Production of spin-polarized RI beam with RIKEN Projectile fragment Separator (RIPS) RIPS RIPS K=540 RIKEN Ring Cyclotron • Isotope separation • magnetic analysis (A/Z) • + • momentum-loss analysis (A2.5/Z1.5) • Production of spin polarization • scattering-angle selection • + • momentum analysis

  11. PSTP2007 Sept. 10-15 at BNL e- e- e- e- e- e- e- e- e- e- e- e- β-NMR apparatus θc-axis = 55° c-axis q∝(3cos2θc-1) = 0 α-Al2O3 (sapphire) single crystal (1-AP) (1+AP) (1+AP) (1-AP) • β-ray angular distribution: • W(θ)=1+APcosθ • A: Asymmetry parameter • P: Polarization (U/D)RFoff = (U/D)RFoff = NMR RF coil β-NMR method:K. Sugimoto et al., J. Phys. Soc. Japan 21 (1966) 213.

  12. PSTP2007 Sept. 10-15 at BNL μ [30-32Al] 32Al 31Al 30Al error & correction Δν/ν0 (fitting) ～0.21 (%) Δν/ν0 (F.G. control) ～0.014 (%) ΔB0/B0～0.06 (%) ΔνQ/ν0～0.09 (%) chemical shift < 0.00002 (%) |g[31Al]|=1.529(3) |g[32Al]|=1.951(5) |μ(30AlGS;3+)|=3.010(7) 31Al: D. Borremans et al., PLB 537, 45 (2002) 30, 32Al: H. Ueno et al., PLB 615, 186 (2005)

  13. PSTP2007 Sept. 10-15 at BNL Q [31Al, 32Al] measurements (U/D) RF-on / (U/D)RF-off νQ (kHz) Q[31Al] = 104(9) mb (preliminary) Q[32Al] = 24(2) mb D. Kameda et al., Phys. Lett. B 647, 93 (2007) D. Kameda et al., to be published

  14. PSTP2007 Sept. 10-15 at BNL Systematic comparison with shell model calculations Jp 3+ 5+ 3+ 5/2+ 1+ 5/2+ 5/2+ 5/2+ • The conventional shell model calculation with the full sd model space well reproduce Q(32Al), while the sd model overestimates Q(31Al) by 45%. • The reported Q-moments of 26-28Al are • consistent with the sd shell model. (ep,en)=(1.3,0.5) |Q| moment (emb) Present results • The m-moments are well reproduced by the conventional sd-shell model. • The Monte Carlo shell model calculations predict that the Q-moments of 33Al and 34Al are significantly enhanced by the mixing of the pf-intruder configurations. |m| moment (mN) Experimentally, there is no evidence for the pf-intruder structure in the ground states of N=18-19 Al isotopes.

  15. PSTP2007 Sept. 10-15 at BNL Summary • The polarization is typically 1~10%, which strongly depends on • emission angle and outgoing momentum of the fragment • target-Z numbers ( competition of far-side and near-side trajectories) • removed-nucleon numbers in the fragmentation • From recent measurements • Sufficient polarization induced by DA~10 fragmentations • The nuclear moments provide useful information about nuclear structure far from the stability, island of inversion. Future: RI beam Factory in RIKEN

  16. Thank you.

  17. PSTP2007 Sept. 10-15 at BNL Isospin-dependent effective chrages Polarization charges: Nuclear structure Vol. II Aage Bohr, Ben R. Mottelson c t =0 = 1.0 c t =1 = -5/8 V1/V0=130MeV/-50MeV=-2.6 j orbit with Woods-saxon potential • The overestimation of Q(31Al) is reduced. • In the other Al isotopes, the consistency between experiment and theory is preserved, except for the case of 28Al. Further analysis is now in progress. Isopin-dep. (ep, en)

  18. PSTP2007 Sept. 10-15 at BNL Measurements of the Q moments α-Al2O3 (sapphire) single crystal νL∼7MHz ∆ν[eqQ]∼100kHz α-Al2O3 Zeeman eqQ RF sweeps for OneQ-moment data point 31Al Iπ=5/2+ 63ms

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